[WIP] Fix BinaryExporter deserialization for multiple UserData lists

jme3-core/src/main/java/com/jme3/scene/UserData.java

@@ -74,8 +74,20 @@ public final class UserData implements Savable {
     private static final int   TYPE_SHORT        = 10;
     private static final int   TYPE_BYTE         = 11;
 
+    // Counter for generating unique IDs to prevent field name collisions
+    private static final java.util.concurrent.atomic.AtomicLong uniqueIdCounter = 
+        new java.util.concurrent.atomic.AtomicLong(0);
+
+    // Prefix used for backwards compatibility with files created before the uniqueId field was added
+    private static final String LEGACY_PREFIX = "0";
+
     protected byte             type;
     protected Object           value;
+
+    // Unique identifier for this UserData instance to prevent field name collisions
+    // when multiple UserData objects with lists/maps/arrays are serialized together.
+    // Marked volatile to ensure visibility across threads during concurrent serialization.
+    private transient volatile String uniqueId;
 
     public UserData() {
     }
@@ -139,6 +151,19 @@ public void write(JmeExporter ex) throws IOException {
         OutputCapsule oc = ex.getCapsule(this);
         oc.write(type, "type", (byte) 0);
 
+        // Generate a unique ID for this instance to prevent field name collisions
+        // when multiple UserData objects with lists/maps/arrays are serialized together.
+        // Store it so it can be read back during deserialization.
+        // Use double-checked locking to ensure thread-safety.
+        if (uniqueId == null) {
+            synchronized (this) {
+                if (uniqueId == null) {
+                    uniqueId = String.valueOf(uniqueIdCounter.incrementAndGet());
+                }
+            }
+        }
+        oc.write(uniqueId, "uniqueId", null);
+
         switch (type) {
             case TYPE_INTEGER:
                 int i = (Integer) value;
@@ -165,15 +190,15 @@ public void write(JmeExporter ex) throws IOException {
                 oc.write(sav, "savableVal", null);
                 break;
             case TYPE_LIST:
-                this.writeList(oc, (List<?>) value, "0");
+                this.writeList(oc, (List<?>) value, uniqueId + ":0");
                 break;
             case TYPE_MAP:
                 Map<?, ?> map = (Map<?, ?>) value;
-                this.writeList(oc, map.keySet(), "0");
-                this.writeList(oc, map.values(), "1");
+                this.writeList(oc, map.keySet(), uniqueId + ":0");
+                this.writeList(oc, map.values(), uniqueId + ":1");
                 break;
             case TYPE_ARRAY:
-                this.writeList(oc, Arrays.asList((Object[]) value), "0");
+                this.writeList(oc, Arrays.asList((Object[]) value), uniqueId + ":0");
                 break;
             case TYPE_DOUBLE:
                 Double d = (Double) value;
@@ -196,6 +221,16 @@ public void write(JmeExporter ex) throws IOException {
     public void read(JmeImporter im) throws IOException {
         InputCapsule ic = im.getCapsule(this);
         type = ic.readByte("type", (byte) 0);
+
+        // Read the unique ID that was written during serialization
+        uniqueId = ic.readString("uniqueId", null);
+
+        // For backwards compatibility with old files that don't have uniqueId,
+        // use the original prefix. This matches the field names in old files.
+        if (uniqueId == null) {
+            uniqueId = "0";
+        }
+
         switch (type) {
             case TYPE_INTEGER:
                 value = ic.readInt("intVal", 0);
@@ -216,19 +251,19 @@ public void read(JmeImporter im) throws IOException {
                 value = ic.readSavable("savableVal", null);
                 break;
             case TYPE_LIST:
-                value = this.readList(ic, "0");
+                value = this.readList(ic, uniqueId + ":0");
                 break;
             case TYPE_MAP:
                 Map<Object, Object> map = new HashMap<>();
-                List<?> keys = this.readList(ic, "0");
-                List<?> values = this.readList(ic, "1");
+                List<?> keys = this.readList(ic, uniqueId + ":0");
+                List<?> values = this.readList(ic, uniqueId + ":1");
                 for (int i = 0; i < keys.size(); ++i) {
                     map.put(keys.get(i), values.get(i));
                 }
                 value = map;
                 break;
             case TYPE_ARRAY:
-                value = this.readList(ic, "0").toArray();
+                value = this.readList(ic, uniqueId + ":0").toArray();
                 break;
             case TYPE_DOUBLE:
                 value = ic.readDouble("doubleVal", 0.);

jme3-plugins/src/test/java/com/jme3/export/JmeExporterTest.java

@@ -139,7 +139,7 @@ public void testSaveWithNullParent() throws IOException {
     public void testExporterConsistency() {
         //
         final boolean testXML = true;
-        final boolean testLists = false;
+        final boolean testLists = true;
         final boolean testMaps = true;
         final boolean printXML = false;